Actuator unit for an electromechanically actuatable disk brake

ABSTRACT

An actuating unit for an electromechanically actuatable disk brake for motor vehicles consists essentially of a drive unit ( 1 ), i.e., an electric motor ( 11 ); an actuating element ( 7 ), by means of which one ( 4 ) of two friction linings ( 4, 5 ) mounted with limited freedom of movement in a brake caliper can be brought into engagement with a brake disk ( 6 ); and a first and a second reducing gear ( 2, 3 ). An electronic controller ( 8 ), which serves to drive the electric motor ( 11 ), is assigned to the actuating unit.  
     To realize an actuating unit of compact axial dimensions which is also optimally designed with respect to packaging, at least part of the electronic controller ( 8 ) is mounted between the electric motor ( 11 ) and the housing ( 25 ) which holds the second reducing gear ( 3 ).

BACKGROUND OF THE INVENTION

The invention pertains to an actuating unit for an electromechanicallyactuatable disk brake for motor vehicles, the unit being mounted on abrake caliper. Two friction linings, each of which works together withone of the lateral surfaces of a brake disk, are mounted in the caliperwith freedom to move within a limited range. An actuating element of theactuating unit brings one of the friction linings into engagement withthe brake disk directly, whereas the other friction lining is broughtinto engagement with the brake disk indirectly through the action of thereaction force applied by the brake caliper. The actuating unit consistsof an electric motor; a first reducing gear, which acts between theelectric motor and the actuating element; and a second reducing gear,which acts between the electric motor and a part of the first reducinggear. The actuating unit also has an electronic controller, which servesto drive the electric motor.

An electromechanical actuating unit of this type is known fromInternational Patent Application WO 00/61962. In the previously knownactuating unit, the electronic controller is structurally separate fromthe actuating unit and is located apart from it.

The previously known actuating unit suffers in particular from thedisadvantage that electrical lines with large cross sections arerequired to transmit the required electric power or current for all ofthe brake functions (service brake and parking braking functions). As aresult, the distance between the actuating unit and the associatedelectronic controller is considered critical, especially when abrushless electric motor is used. The separate arrangement of thepreviously mentioned components also causes considerable problems withrespect to packaging.

It is therefore the task of the present invention to propose anelectromechanical actuating unit of the general type indicated abovewhich is characterized by a significant reduction in the distancebetween the actuating unit and its associated electronic controller andby an optimized design with respect to packaging.

SUMMARY OF THE INVENTION

This task is accomplished according to the invention in that at leastpart of the electronic controller is mounted between the electric motorand the housing which holds the second reducing gear.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below in the followingdescription of an exemplary embodiment with reference to the attacheddrawing:

FIG. 1 shows an axial cross section of an embodiment of the inventiveelectromechanical actuating unit;

FIG. 2 shows a partial cross-sectional view of a first variant of theinventive electromechanical actuating unit; and

FIG. 3 shows a partial cross-sectional view of a second variant of theinventive electromechanical actuating unit.

DETAILED DESCRIPTION OF THE DRAWINGS

The inventive electromechanical actuating unit shown in the drawing isused to actuate a floating-caliper disk brake. The caliper of the brake,which is shown merely in schematic fashion, is supported with a certainfreedom of movement in a stationary bracket (not shown). Two frictionlinings 4, 5 are mounted in the brake caliper in such a way that onefaces the left, the other the right, lateral surface of a brake disk 6.

In the following, the friction lining 4 on the right in the drawing isreferred to as the first friction lining, and the other friction lining,designated 5, is referred to as the second friction lining. Whereas thefirst friction lining 4 can be brought into engagement directly with thebrake disk 6 by the actuating unit 7, the second friction lining 5 ispushed against the opposite lateral surface of the brake disk 6 by theaction of the reaction force applied by the brake caliper when thearrangement is actuated. The inventive actuating unit, which is attachedto the brake caliper by fastening means (not shown), has a modulardesign and consists essentially of four independent assemblies ormodules, namely, a drive unit 1; a first reducing gear 2, which actuatesthe first friction lining 4; a second reducing gear 3, which actsbetween the drive unit 1 and the first reducing gear 2; and anelectronic controller 8.

The previously mentioned drive unit 1 consists of an electric motor 11,which, in the example illustrated here, is designed as an electronicallycommutated motor excited by permanent magnets, the stator 9 of which ismounted permanently in a motor housing 12. The rotor 10 is connected toa shaft 13, which is in working connection with the second reducing gear3. The first reducing gear 2 in the example shown here is designed as aball screw, which is mounted in a gearbox housing 14. This housing couldalso be designed as an integral part of the previously mentioned brakecaliper. The ball screw consists here of a threaded nut 16 and athreaded spindle 17. Several balls (not designated by a reference no.)are installed between the threaded nut 16 and the threaded spindle 17.These balls revolve when the threaded spindle 17 turns and cause thethreaded nut to move in the axial or translational direction. Thethreaded nut 16 is preferably made up of two parts, namely, a first part18, which forms the previously mentioned actuating element 7, and asecond part 19, which includes a return area for the balls, which allowsthe balls to roll back load-free to the beginning of the raceway whichcarries them. It can also be derived from the drawing that the secondreducing gear 3 is designed as an epicyclic gear.

The arrangement is preferably designed so that the rotor 10, i.e., theshaft 13, of the electric motor 11, acting by way of the second reducinggear 3, drives the threaded spindle 17, while the first part 18 of thethreaded nut 16 is supported against the first friction lining 4. Thefirst reducing gear 2 is coupled to the second reducing gear 3 by meansof a torque-free plug-in connection, designated by the reference number20, which, for example, can be designed as two sets of serrations. Tworadial bearings 21, 22, which are installed in the motor housing,support the rotor 10.

As can also be seen in FIG. 1, the electronic controller 8 has a housing23, made preferably of plastic, which is provided with a flange 24. Ascan be seen especially clearly in FIG. 2, this flange holds all of theelectrical interfaces between the electric motor 11 and the electroniccontroller 8 and all of the mechanical interfaces between the electricmotor 11 and the second reducing gear 3. The flange 24 is advantageouslylocated between the electric motor 11 and the housing 25 which holds thesecond reducing gear 3. A position-detecting system (not shown here) isused to determine the actual position of the rotor 10.

As can be seen especially in FIGS. 2 and 3, the position-detectingsystem is formed essentially by an encoder wheel 26, mounted on theshaft 13, and a sensor element 27. A Hall sensor, for example, or amagnetoresistive element can be used as the sensor element 27. In theembodiment shown in FIG. 2, the sensor element 27 is connectedpermanently to the housing 23 of the electronic controller 8, i.e., toits flange 24. In another embodiment (not shown), the sensor element ismounted with a certain limited freedom of movement with respect to thehousing of the electronic controller and is connected to it by means ofan elastic fastening. The previously mentioned electrical interfacebetween the electric motor 11 and the electronic controller 8, whichserves to supply power to the electric motor 11, is, in the exampleshown here, designed as a plug-and-socket connection 28, 29. The plug ormale part 28 is assigned to the electric motor 11 and is designed as acomponent of an end plate 30, which holds the bearing 31 which supportsthe shaft 13. In contrast, the socket or female part 29 is assigned tothe electronic controller 8 and is designed as a component of the flange24, preferably molded into the flange 24. The electrical lines 32connecting the sensor element 27 to other components of the electroniccontroller 8 are embedded in the plastic of which the housing 23 of theelectronic controller 8 is made.

In the modified embodiment shown in FIG. 3, the sensor element 27 isintegrated into the previously mentioned end plate 30. The plug or malepart 28 a not only supplies power to the electric motor 11 but alsoprovides the contact for the sensor element 27.

Numerous modifications are, of course, possible without abandoning thescope of the present invention. For example, the electric motor servingas the drive unit 1 could also be designed as a switched reluctancemotor (SR-motor). Other designs of the epicyclic gear are alsoconceivable, such as, for example, a two-stage differential epicyclicgear or a gear with planet wheels which engage by their first stage witha sun wheel and by their second stage with an internal gearwheel bymeans of intermediate spur gearwheels. Conceivable also, of course, aregears which produce large reductions by means of a deformable, toothedring and an eccentric arrangement.

1-18. (canceled)
 19. An actuating unit for an electromechanicallyactuatable disk brake for motor vehicles mounted on a brake caliper,with two friction linings (4, 5) being mounted in the caliper withfreedom to move within a limited range, each of which works togetherwith one of the lateral surfaces of a brake disk (6), where an actuatingelement (7) of the actuating unit brings one of the friction linings (4)into engagement with the brake disk (6) directly, whereas the otherfriction lining (5) is brought into engagement with the brake disk (6)indirectly through the action of the reaction force applied by the brakecaliper, where the actuating unit consists of an electric motor (11); afirst reducing gear (2), which acts between the electric motor (11) andthe actuating element (7); and a second reducing gear (3), which actsbetween the electric motor (11) and a part of the first reducing gear(2) and is held in place by a housing, and where an electroniccontroller, which serves to drive the electric motor, is also assignedto the actuating unit, wherein at least part of the electroniccontroller (8) is mounted between the electric motor (11) and thehousing (25) which holds the second reducing gear (3).
 20. The actuatingunit according to claim 19, wherein the electronic controller (8) has ahousing (23) with a flange (24), which is mounted between the electricmotor (11) and the housing (25) for the second reducing gear (3) andholds all of the electrical interfaces between the electric motor (11)and the electronic controller (8) and the mechanical interfaces betweenthe electric motor (11) and the second reducing gear (3).
 21. Theactuating unit according to claim 20, wherein the electrical interfacebetween the electric motor (11) and the electronic controller (8) isdesigned as a plug-and-socket connection (28, 29).
 22. The actuatingunit according to claim 21, wherein the electrical interface (28, 29)serves to supply power to the electric motor (11).
 23. The actuatingunit according to claim 21, wherein the plug or male part (28) isassigned to the electric motor (11), whereas the socket or female part(29) is assigned to the electronic controller (8).
 24. The actuatingunit according to claim 23, wherein the socket or female part (29) ismolded into the flange (24).
 25. The actuating unit according claim 19,wherein the electric motor (11) is designed as a brushless,electronically commutated direct-current motor, and wherein sensorarrangement (26, 27) is provided for sensing the position of the rotorof the electric motor (11).
 26. The actuating unit according to claim 7,wherein the sensor arrangement (26, 27) for sensing the position of therotor of the electric motor (11) comprises an encoder wheel (26) mountedon the shaft (13) of the electric motor (11) and a sensor element (27),which cooperates with the encoder wheel (26).
 27. The actuating unitaccording to claim 26, wherein the sensor element (27) is permanentlyconnected to the housing (23) of the electronic controller (8).
 28. Theactuating unit according to claim 26, wherein the sensor element (27) ismounted with a certain limited freedom of movement with respect to thehousing (23) of the electronic controller (8) and is connected to it bymeans of an elastic fastening.
 29. The actuating unit according to claim26, wherein the sensor element (27) is mounted on an end plate (30),which closes off the electric motor (11), carries an electricalconnector (28), and serves to support the shaft (13) of the electricmotor (11).
 30. The actuating unit according to claim 29, wherein theelectrical connector is a plug (28) which serves as an electricalcontact for the sensor element (27).
 31. The actuating unit according toclaim 19, wherein a torque-free plug-in connection (20), is providedbetween the first (2) and the second reducing gear (3).
 32. Theactuating unit according to claim 31, wherein the plug-in connection(20) is designed at the end of the drive element (spindle) (17) of thefirst reducing gear (2).
 33. The actuating unit according to claim 19,wherein the electric motor (11) and a part of the second reducing gear(3) are radially offset from the longitudinal axis of the first reducinggear (2).
 34. The actuating unit according to claim 33, wherein theelectric motor (11) and a part of the second reducing gear (3) areaxially parallel to the longitudinal axis of the first reducing gear(2).
 35. The actuating unit according to claim 19, wherein an additionalelectrical interface is provided between the first gear and the secondgear to connect electrically a force-sensing element mounted in thefirst gear to the electronic controller.
 36. The actuating unitaccording to claim 35, wherein the interface also serves the additionalpurpose of fastening the electronic controller mechanically to the brakecaliper.